Semiconductor processing methods of forming a conductive projection and methods of increasing alignment tolerances

ABSTRACT

Semiconductor processing methods of forming conductive projections and methods of increasing alignment tolerances are described. In one implementation, a conductive projection is formed over a substrate surface area and includes an upper surface and a side surface joined therewith to define a corner region. The corner region of the conductive projection is subsequently beveled to increase an alignment tolerance relative thereto. In another implementation, a conductive plug is formed over a substrate node location between a pair of conductive lines and has an uppermost surface. Material of the conductive plug is unevenly removed to define a second uppermost surface, at least a portion of which is disposed elevationally higher than a conductive line. In one aspect, conductive plug material can be removed by facet etching the conductive plug. In another aspect, conductive plug material is unevenly doped with dopant, and conductive plug material containing greater concentrations of dopant is etched at a greater rate than plug material containing lower concentrations of dopant.

TECHNICAL FIELD

This invention relates to semiconductor processing methods of formingconductive projections, and to methods of increasing alignmenttolerances.

BACKGROUND OF THE INVENTION

As dimensions of semiconductor devices continue to shrink, alignment ofindividual device components, and compensation for misalignment becomeincreasingly important. Problems associated with feature misalignmentcan cause shorting and other catastrophic device failure.

In forming semiconductor devices, it is not uncommon to use a conductiveprojection of material such as a conductive plug to form an intermediateelectrical connection between a substrate node location and a devicecomponent. An exemplary conductive projection is shown in FIGS. 1-3.

Referring to FIG. 1, a semiconductor wafer fragment is shown generallyat 20 and comprises a semiconductive substrate 22. In the context ofthis document, the term "semiconductive substrate" is defined to meanany construction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term "substrate" refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above.

A pair of isolation oxide regions 24 are formed over substrate 22. Aplurality of conductive lines 26 are provided and typically include apolysilicon layer 28, a silicide layer 30 and an insulative cap 32.Sidewall spacers 34 are provided over conductive and non-conductiveportions of line 26. Diffusion regions 35 are provided and constitutenode locations with which electrical communication is desired. Waferfragment 20 comprises a portion of a dynamic random access memory (DRAM)device. Conductive projections 36 are provided. A centermost of theconductive projections 36 is positioned to establish electricalcommunication between diffused regions and a bit line yet to be formed.The conductive projections are typically formed within an opening in aninsulative oxide layer such as borophosphosilicate glass (BPSG), andsubsequently planarized. A layer 38 is formed over substrate 22 andcomprises an insulative material such as BPSG.

Referring to FIG. 2, a pair of contact openings 40 are formed throughlayer 38 and outwardly expose the illustrated projections 36. Contactopenings 40 constitute openings within which storage capacitors are tobe formed. Such capacitors are typically formed by providing a layer ofconductive material within opening 40 and over layer 38, andsubsequently depositing a capacitor dielectric layer and cell platelayer thereover.

Referring to FIG. 3, an enlarged portion of FIG. 2 shows an examplealignment tolerance X between centermost conductive projection 36 and adashed extension of the right edge of one opening 40. A misalignment ofthe mask used to form contact opening 40 which is greater than X, and inthe direction of the conductive projection, can result in overlap ofcontact opening 40 and centermost conductive projection 36. Such wouldsubsequently cause conductive capacitor material provided into contactopening 40 to be shorted with centermost conductive projection 36thereby rendering this portion of the device inoperative.

This invention arose out of concerns associated with increasingalignment tolerances between conductive projections and electricalcomponents formed over a semiconductor wafer. The artisan willappreciate other applicability, with the invention only being limited bythe accompanying claims appropriately interpreted in accordance with thedoctrine of equivalents.

SUMMARY OF THE INVENTION

Semiconductor processing methods of forming conductive projections andmethods of increasing alignment tolerances are described. In oneimplementation, a conductive projection is formed over a substratesurface area and includes an upper surface and a side surface joinedtherewith to define a corner region. The corner region of the conductiveprojection is subsequently beveled to increase an alignment tolerancerelative thereto. In another implementation, a conductive plug is formedover a substrate node location between a pair of conductive lines andhas an uppermost surface. Material of the conductive plug is unevenlyremoved to define a second uppermost surface, at least a portion ofwhich is disposed elevationally higher than a conductive line. In oneaspect, conductive plug material can be removed by facet etching theconductive plug. In another aspect, conductive plug material is unevenlydoped with dopant, and conductive plug material containing greaterconcentrations of dopant is etched at a greater rate than plug materialcontaining lower concentrations of dopant.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with prior art methods.

FIG. 2 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown in FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 2.

FIG. 4 is a view of a semiconductor wafer fragment in process inaccordance with one embodiment of the invention.

FIG. 5 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 4.

FIG. 6 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 5.

FIG. 7 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 6.

FIG. 8 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 7.

FIG. 9 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 8.

FIG. 10 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 9.

FIG. 11 is a view of the FIG. 4 wafer fragment at a processing stepsubsequent to that shown in FIG. 10.

FIG. 12 is a view of the FIG. 10 wafer fragment at a processing step inaccordance with another embodiment of the invention.

FIG. 13 is a view of the FIG. 12 wafer fragment at a processing stepsubsequent to that shown in FIG. 12.

FIG. 14 is a view of either of the FIGS. 11 or 13 wafer fragments, at aprocessing step subsequent to that shown in either of the respectivefigures.

FIG. 15 is a view of the FIG. 14 wafer fragment at a processing stepsubsequent to that shown in FIG. 14.

FIG. 16 is a view of the FIG. 14 wafer fragment at a processing stepsubsequent to that shown in FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws "to promote the progressof science and useful arts" (Article 1, Section 8).

Referring to FIG. 4, a semiconductor wafer fragment in process inaccordance with one embodiment of the invention is shown generally at 42and comprises a semiconductive substrate 44. A pair of conductive lines46 are formed over substrate 44 and comprise a polysilicon layer 48, asilicide layer 50 and an insulative cap 52. Sidewall spacers 54 areprovided over conductive and non-conductive portions of lines 46. Lines46 constitute a pair of spaced-apart, insulated conductive lines whichdefine a node location 56 or surface area therebetween with whichelectrical communication is desired. In the illustrated and preferredembodiment, node location 56 comprises a diffusion region 57 to beconnected with a bit line. Other node locations are defined by diffusionregions 57 laterally outward of node location 56, and comprise locationswith which electrical communication with storage capacitors is desired,as will become apparent below. A first insulative layer 58 is formedover node location 56 and between the conductive lines. An exemplarymaterial for layer 58 is BPSG.

Referring to FIG. 5, layer 58 is planarized as by chemical mechanicalpolishing to provide a generally planar upper surface 60. Theplanarization of layer 58 can be made to stop on or over the insulativecaps of the conductive lines.

Referring to FIG. 6, a second layer of insulative material 62 is formedover node location 56 and has a generally planar upper surface 64.

Referring to FIG. 7, a patterned masking layer 66 is formed oversubstrate 44.

Referring to FIG. 8, openings 68 are formed through material of bothfirst and second layers 58, 62 to proximate the node locations.Preferably, the openings are sufficient to expose the node locationsover which each is formed.

Referring to FIG. 9, conductive material 70 is formed over thesubstrate, insulative material 62, and within openings 68. The openingsare preferably filled with conductive material. An exemplary conductivematerial is polysilicon.

Referring to FIG. 10, conductive material 70 is planarized relative toinsulative layer upper surface 64. Such isolates conductive materialwithin openings 68 and provides planarized conductive projections 72over the substrate. In the illustrated and preferred embodiment,conductive projections 72 constitute conductive plugs which are formedin connection with formation of DRAM circuitry. Individual conductiveprojections 72 include respective upper or uppermost surfaces 74 whichare joined with respective side surfaces 76. The side surfaces projectaway from the node location over which each is formed and terminateproximate the respective surface 74 with which it joins. Joinder betweenupper and side surfaces 74, 76 defines corner regions of the individualconductive projections. Intermediate and away from the corner regions ofeach projection is a central region 78.

Preferably and as shown, the individual conductive plugs project awayfrom the respective node locations over which each is formed a distancewhich is further than a distance that one of the conductive linesprojects away from the node location. Accordingly, each plug's uppermostsurface is disposed elevationally over both conductive lines and issubstantially coplanar with the generally planar portion of insulativematerial 62.

Referring to FIG. 11, corner regions of the conductive projections arebeveled. In the illustrated example, the beveling of the corner regionscomprises facet etching the conductive projection to provide theillustrated beveled construction. Such etching can take place in a coldwall processing chamber using an unheated chuck. Other conditionsinclude a power setting of between 100 W to 600 W, a pressure setting ofbetween 10 to 100 mTorr, and use of Argon ions preferably havingincident angles of between 45° to 60°. The insulative material can beremoved prior to the facet etching. Alternately, the insulative materialcan remain during the facet etching.

The facet etching of the conductive projection constitutes unevenlyremoving the conductive material sufficient to define a second uppermostsurface 80, at least of portion of which is disposed elevationallyhigher than the conductive lines. In this example, more material isremoved from the corner region than from the central region of eachplug, and second uppermost surface 80 is generally non-planar.

Referring to FIG. 12, a second embodiment is shown, with the discussionproceeding with processing subsequent to the FIG. 10 wafer fragment. Inthis example, the conductive projections are unevenly doped proximatethe upper and side surfaces. Such uneven doping can be accomplishedusing an angled ion implant at energies between about 20 keV to 1000keV, and angles greater than 0° and less than about 60°. The angled ionimplant subjects the corner regions to a greater degree of normal angleimplanting such that greater implanting occurs relative to the cornerregions as opposed to the upper surfaces. As a result, outermost sideportions, e.g. the corner regions, of the conductive plug have greaterconcentrations of dopant than plug material therebetween proximate thecentral region. Insulative material 62 (FIG. 10) can be removed prior todoping the conductive plugs, or remain during the doping.

Referring to FIG. 13, the individual conductive plugs have been beveled.Such can be accomplished by etching material of the conductive plugs orprojections containing greater concentrations of dopant at a greaterrate than material of the conductive projections containing lowerconcentrations of dopant. Insulative material 62 (FIG. 10) can beremoved prior to the etching of the conductive plugs or remain duringthe etching. The beveling of the conductive plugs comprises unevenlyremoving material of the conductive plug to define a second uppermostsurface 80a, at least a portion of which is disposed elevationallyhigher than the conductive lines. Exemplary etching can comprise dry orwet etching of the plug material. In the former, Cl₂ or HB chemistriescan be used to sufficiently activate etching of the corner regions. Inthe latter, wet etches with a sufficiently high pH can be used. Examplesinclude TMAH or SCI (APM).

Referring to FIG. 14, a layer of material 82 is formed over thesubstrate, with BPSG being but one example.

Referring to FIG. 15, openings 84 are formed over the substrate anddefine a second alignment tolerance X₁ which is greater than the firstalignment tolerance X (FIG. 3).

Referring to FIG. 16, conductive material 86 has been formed over, andis in electrical communication with the leftmost and rightmostconductive plugs and the respective diffusion regions over which theplugs are formed. Conductive material 86 constitutes respective storagenode layers. Dielectric layers 88 are formed over the respective storagenode layers 86, and a cell plate layer 90 is formed over the respectivedielectric layers. Conductive material 94 is formed over, and is inelectrical communication with the centermost conductive plug and thediffusion region over which it is formed. Conductive material 94comprises a bit line. Here, the alignment tolerance between bit linecontact material and adjacent storage capacitors is increased.

Advantages of the above-described methods and structures include thatalignment tolerances can be increased with only a slight modification ofthe processing flow. Process viability can be improved for shifts whichmay occur in or during photo alignment. Additionally, the above methodsallow scaling of contemporary technology to smaller generations ofdevices.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A semiconductor processing method of forming aconductive projection comprising:providing a substrate having a surfacearea over which a conductive projection is to be formed; forming aconductive projection over the surface area, the projection having anupper surface and a side surface joined therewith defining a cornerregion; and beveling the corner region of the conductive projection,insulative material being received against the side surface at thecorner region at the start of the beveling.
 2. A semiconductorprocessing method of forming a conductive projectioncomprising:providing a substrate having a surface area over which aconductive projection is to be formed; forming a conductive projectionover the surface area, the projection having an upper surface and a sidesurface joined therewith defining a corner region; beveling the cornerregion of the conductive projection; wherein the surface area comprisesa diffusion region, and further comprising after the beveling of thecorner region, forming conductive material over the beveled cornerregion of the conductive projection and in electrical communication withthe diffusion region; and further comprising insulative material beingreceived against the side surface at the corner region at the start ofthe beveling.
 3. A semiconductor processing method of forming aconductive projection comprising:providing a substrate having a surfacearea over which a conductive projection is to be formed; forming aconductive projection over the surface area, the projection having anupper surface and a side surface joined therewith defining a cornerregion; beveling the corner region of the conductive projection; andwherein the beveling of the corner region comprises:unevenly dopingmaterial of the conductive projection proximate the upper and sidesurfaces thereof; etching material of the conductive projectioncontaining greater concentrations of dopant at a greater rate thanmaterial of the conductive projection containing lower concentrations ofdopant; and further comprising insulative material being receivedagainst the side surface at the corner region at the start of thebeveling.
 4. A semiconductor processing method of forming a conductiveprojection comprising:forming a pair of spaced-apart, insulatedconductive lines over a substrate, the conductive lines defining a nodelocation therebetween with which electrical communication is desired;forming insulative material over the node location and between theconductive lines; forming an opening through the insulative material andbetween to the lines to proximate the node location; forming conductivematerial within the opening over the node location, the conductivematerial having side surfaces which project away from the node locationand terminate proximate an upper surface, the side surfaces and uppersurface defining at least one corner region; beveling the corner region;and further comprising insulative material being received against atleast one side surface at the corner region at the start of thebeveling.